U.S. patent application number 11/987756 was filed with the patent office on 2009-01-01 for interdigital capacitor.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Min Lin Lee, Chin Sun Shyu, Cheng Hua Tsai, Chang Lin Wei.
Application Number | 20090002916 11/987756 |
Document ID | / |
Family ID | 40160135 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090002916 |
Kind Code |
A1 |
Wei; Chang Lin ; et
al. |
January 1, 2009 |
Interdigital capacitor
Abstract
An interdigital capacitor includes a first finger electrode
structure and a second finger electrode structure. The first finger
electrode structure has a first electrode and a plurality of first
extending electrodes. The first extending electrodes are linearly
disposed and arranged. The second finger electrode structure has a
second electrode and a plurality of second extending electrodes.
The second extending electrodes are linearly disposed and arranged.
The second finger electrode structure interlaces with the first
finger electrode structure. At least one pair of first coupling
electrodes extend respectively from the neighboring first and
second extending electrodes and are disposed between them.
Inventors: |
Wei; Chang Lin; (Hsinchu,
TW) ; Shyu; Chin Sun; (Hsinchu, TW) ; Tsai;
Cheng Hua; (Hsinchu, TW) ; Lee; Min Lin;
(Hsinchu, TW) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20043-9998
US
|
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
Hsinchu
TW
|
Family ID: |
40160135 |
Appl. No.: |
11/987756 |
Filed: |
December 4, 2007 |
Current U.S.
Class: |
361/303 |
Current CPC
Class: |
H01G 4/005 20130101;
H01G 4/33 20130101 |
Class at
Publication: |
361/303 |
International
Class: |
H01G 4/005 20060101
H01G004/005 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2007 |
TW |
96123306 |
Claims
1. An interdigital capacitor, comprising: a first finger electrode
structure which includes a first electrode and a plurality of first
extending electrodes extending from said first electrode, the first
extending electrodes being linearly disposed and arranged; a second
finger electrode structure which includes a second electrode and a
plurality of second extending electrodes extending from said second
electrode, the second extending electrodes being linearly disposed
and arranged, wherein said second finger electrode structure
interlaces with said first finger electrode structure; and at least
one pair of first coupling electrodes extending respectively from
the neighboring first and second extending electrodes, being
disposed between said first and second extending electrodes.
2. The interdigital capacitor of claim 1, wherein the capacitor is
disposed on any one of: the surface of a coplanar substrate, and
within a substrate, said substrate being a printed circuit
substrate, a ceramic substrate, or an integrated circuit
substrate.
3. The interdigital capacitor of claim 1, wherein the capacitor is
disposed on any one of: the surface of a coplanar substrate, and
within a substrate, said substrate being composed of multiple
stacked dielectric materials.
4. The interdigital capacitor of claim 1, wherein the plurality of
first extending electrodes and the plurality of second extending
electrodes are parallel to one another.
5. The interdigital capacitor of claim 1, wherein the plurality of
first extending electrodes and the plurality of second extending
electrodes are not parallel to one another.
6. The interdigital capacitor of claim 1, wherein the at least one
pair of first coupling electrodes are geometric-shaped.
7. The interdigital capacitor of claim 6, wherein the at least one
pair of first coupling electrodes can be any one of:
rectangular-shaped, triangular-shaped, taper-shaped,
circular-shaped, and oval-shaped.
8. The interdigital capacitor of claim 1, wherein at least one pair
of first coupling electrodes are any one of: wavy-shaped and
L-shaped.
9. The interdigital capacitor of claim 1, wherein one electrode of
the first coupling electrodes parallels the other electrode of the
first coupling electrodes, and the first coupling electrodes extend
respectively from the first extending electrode and from the second
extending electrode.
10. The interdigital capacitor of claim 1, wherein a pair of second
coupling electrodes extend respectively and vertically from the
first extending electrode and from the second extending
electrode.
11. The interdigital capacitor of claim 1, wherein one electrode of
the first coupling electrodes parallels the other electrode of the
first coupling electrodes, and a pair of second coupling electrodes
extend respectively and vertically from the first extending
electrode and from the second extending electrode.
12. The interdigital capacitor of claim 10, wherein the second
coupling electrodes are disposed between the first extending
electrode and the second extending electrode in an interlacing
manner.
13. The interdigital capacitor of claim 11, wherein the second
coupling electrodes are disposed between the first extending
electrode and the second extending electrode in an interlacing
manner.
14. The interdigital capacitor of claim 11, wherein the first
coupling electrodes interlace with the second coupling electrodes
and both the first and second coupling electrodes are disposed
between the first extending electrode and the second extending
electrode.
15. The interdigital capacitor of claim 1, wherein the at least one
pair of coupling electrodes comprises a plurality of taper-shaped
coupling electrodes disposed in an interlacing manner.
16. The interdigital capacitor of claim 1, wherein the at least one
pair of the coupling electrodes comprises a plurality of
wavy-shaped coupling electrodes disposed with one concave electrode
and one convex electrode.
17. The interdigital capacitor of claim 1, wherein the at least one
pair of the coupling electrodes comprises a plurality of
triangular-shaped coupling electrodes disposed in an interlacing
manner.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a capacitor, and more
particularly to an interdigital capacitor.
BACKGROUND OF THE INVENTION
[0002] In an age where products of computers, communications and
consumer electronics become more and more popular, consumer
behavior has been an important factor that dominates the trend of
product design. Nowadays, consumer electronic devices have almost
become a part integrated to the human body; contents of various
formats can be accessed through these electronic devices
emphasizing great convenience, low power consumption, compact size
and low cost. For portable or wearable electronic devices, there
are often needs for products that endure bending or curving by
customers, and thus, it is necessary to apply flexible circuits
into these products.
[0003] It is known that capacitors are widely used in circuit
boards, and most of the capacitors are soldered to circuit boards
through a complicated manufacturing process such as surface mount
techniques (SMTs). Although capacitors have generally become
downsized, multiple layers of substrates are still needed to
construct a circuit board, which results in an increase of area and
height of physical circuits. Recently, many research institutes
have endeavored to develop different capacitor materials that
enable capacitors to be embedded in multi-layer circuit substrates,
and some materials have been successfully applied to circuits of
various electronic devices.
[0004] Board bending uses frequently occur to capacitors embedded
in wearable or portable electronic devices. Conventional design for
an interdigital capacitor includes coupling electrodes of only one
direction. As shown in FIG. 1, a conventional interdigital
capacitor 200 comprises a first finger electrode structure 30,
which includes a first electrode 31 and a plurality of first
extending electrodes 32 extending from the first electrode 31, each
of the first extending electrodes 32 paralleling one another; the
conventional interdigital capacitor 200 also comprises a second
finger electrode structure 40, which includes a second electrode 41
and a plurality of second extending electrodes 42 extending from
the second electrode 41, each of the second extending electrodes 42
paralleling one another. Moreover, the second finger electrode
structure 40 interlaces with the first finger electrode structure
30.
[0005] When a conventional interdigital capacitor encounters an
external force that bends its electrode plates, the capacitive
characteristics are subject to change in accordance with the
direction of bending axis since the capacitor includes coupling
electrodes of one direction only.
[0006] Thus, it is quite an urgent demand for the industry to
provide an interdigital capacitor that has more stable capacitive
characteristics after being bent.
SUMMARY OF THE INVENTION
[0007] The present invention provides an interdigital capacitor
structure having coupling electrodes of more than one direction in
order to enhance the stability of capacitance.
[0008] The present invention provides an interdigital capacitor
comprising a first finger electrode structure, which includes a
first electrode and a plurality of first extending electrodes
extending from the first electrode, the first extending electrodes
being linearly disposed and arranged; the interdigital capacitor
also comprises a second finger electrode structure, which includes
a second electrode and a plurality of second extending electrodes
extending from the second electrode, the second extending
electrodes being linearly disposed and arranged. Moreover, the
second finger electrode structure interlaces with the first finger
electrode structure, wherein at least one pair of coupling
electrodes extend respectively from the neighboring first and
second extending electrodes, and the pair of coupling electrodes
are disposed between the neighboring extending electrodes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic drawing of a conventional interdigital
capacitor.
[0010] FIG. 2 is a schematic drawing of an interdigital capacitor
according to a first embodiment of the present invention.
[0011] FIG. 3 is a schematic drawing of an interdigital capacitor
according to a second embodiment of the present invention.
[0012] FIG. 4 is a schematic drawing of an interdigital capacitor
according to a third embodiment of the present invention.
[0013] FIG. 5 is a schematic drawing of an interdigital capacitor
according to a fourth embodiment of the present invention.
[0014] FIG. 6 is a schematic drawing of an interdigital capacitor
according to a fifth embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The interdigital capacitor of one embodiment of the present
invention is disposed on the surface of a coplanar substrate,
comprising a first finger electrode structure, which includes a
first electrode and a plurality of first extending electrodes
extending from the first electrode, the first extending electrodes
being linearly disposed and arranged; the interdigital capacitor
also comprises a second finger electrode structure, which includes
a second electrode and a plurality of second extending electrodes
extending from the second electrode, the second extending
electrodes being linearly disposed and arranged. Moreover, the
second finger electrode structure interlaces with the first finger
electrode structure, wherein at least one pair of first coupling
electrodes extend respectively from the neighboring first and
second extending electrodes, and the coupling electrodes are
disposed between the neighboring extending electrodes. The present
invention enables an interdigital capacitor to comprise coupling
electrodes of more than two directions at a time when it is bent
towards different directions; thus, it can be applied to wearable
or portable electronic devices and still keeps its capacitive
characteristics stable after being bent. The variations on
electrical characteristics can be minimized by employing an
interdigital capacitor of the present invention. The following will
describe different embodiments of the present invention in greater
detail.
[0016] Referring to FIG. 2, a schematic drawing of an interdigital
capacitor according to a first embodiment of the present invention
is shown. The interdigital capacitor 100 of the first embodiment is
disposed on the surface of a coplanar substrate or within a
substrate (not shown), comprising a first finger electrode
structure 10, which includes a first electrode 11 and a plurality
of first extending electrodes 12 extending from the first electrode
100 each of the first extending electrodes 12 paralleling one
another; the interdigital capacitor 100 also comprises a second
finger electrode structure 20, which includes a second electrode 21
and a plurality of second extending electrodes 22 extending from
the second electrode 21, each of the second extending electrodes 22
paralleling one another. Moreover, the second finger electrode
structure 20 interlaces with the first finger electrode structure
10.
[0017] A plurality of pairs of first coupling electrodes 13 extend,
respectively and vertically, from each of the first extending
electrodes 12 and from each of the second extending electrodes 22;
each pair of first coupling electrodes 13 parallel another pair and
form a coupling along the X-direction (vertically). A plurality of
pairs of second coupling electrodes 23 extend, respectively and
vertically, from each of the first extending electrodes 12 and from
each of the second extending electrodes 22. Each pair of second
coupling electrodes 23 interlace with another pair and are disposed
between the first extending electrode 12 and the second extending
electrode 22 to form a coupling along the Y-direction
(horizontally). Furthermore, the first coupling electrodes 13
interlace with the second coupling electrodes 23, and both coupling
electrodes are disposed between the first extending electrode 12
and the second extending electrode 22.
[0018] In this embodiment, the substrate can be, for example, a
printed circuit substrate, a ceramic substrate, an integrated
circuit substrate, or a substrate composed of multiple stacked
dielectric materials, and the shapes of first coupling electrodes
13 or second coupling electrodes 23 can be, for example, square or
rectangular.
[0019] Referring to FIG. 3, a schematic drawing of an interdigital
capacitor according to a second embodiment of the present invention
is shown. The structure of the interdigital capacitor in this
embodiment is approximately identical with that in the first
embodiment. One difference, for example, is that in the second
embodiment, a plurality of L-shaped coupling electrodes 14 extend
vertically from the first extending electrode 12 and from the
second extending electrode 22, wherein the L-shaped coupling
electrodes 14 are disposed in a corresponding manner.
[0020] Referring to FIG. 4, a schematic drawing of an interdigital
capacitor according to a third embodiment of the present invention
is shown. The structure of the interdigital capacitor in this
embodiment is approximately identical with that in the first
embodiment. One difference, for example, is that in the third
embodiment, a plurality of taper-shaped coupling electrodes 15
extend from the first extending electrode 12 and from the second
extending electrode 22, wherein the taper-shaped coupling
electrodes 15 are disposed in an interlacing manner.
[0021] Referring to FIG. 5, a schematic drawing of an interdigital
capacitor according to a fourth embodiment of the present invention
is shown. The structure of the interdigital capacitor in this
embodiment is approximately identical with that in the first
embodiment. One difference, for example, is that in the fourth
embodiment, a plurality of wavy-shaped coupling electrodes 16
extend from the first extending electrode 12 and from the second
extending electrode 22, wherein the wavy-shaped coupling electrodes
16 are disposed with one concave electrode and one convex
electrode.
[0022] Referring to FIG. 6, a schematic drawing of an interdigital
capacitor according to a fifth embodiment of the present invention
is shown. The structure of the interdigital capacitor in this
embodiment is approximately identical with that in the first
embodiment. One difference, for example, is that in the fifth
embodiment, a plurality of triangular-shaped coupling electrodes 17
extend from the first extending electrode 12 and from the second
extending electrode 22, wherein the triangular-shaped coupling
electrodes 17 are disposed in an interlacing manner.
[0023] Compared to the conventional interdigital capacitor shown in
FIG. 1, the interdigital capacitor of the present invention
provides more stable capacitance when the substrate is being bent.
What follows will take the conventional interdigital capacitor
shown in FIG. 1 as an example to demonstrate the variation on
electrical characteristics when the substrate is being bent. The
capacitive characteristics of a conventional interdigital
capacitor, when the capacitor encounters an external force that
bends its electrode plates, are subject to change to an extent in
accordance with the direction of bending. That is, it matters a lot
to the capacitive characteristics whether the bending axis is
vertical or parallel to the electrode plates. A conventional
interdigital capacitor has its capacitance generated from the
coupling electrodes along an X-direction, and the major parameters
that influence the capacitance C of the interdigital capacitor are
the distance S between electrode plates and the length L of each
electrode plate (the amount of coupling on the finger tip region
between the first electrode 31 and the second extending electrode
42, or between the second electrode 41 and the first extending
electrode 32 are very little; the influence is accordingly little
and can thus be ignored hereinafter), wherein:
C=f(S,L),
We define .DELTA.C as the variation of the capacitance.
.DELTA. C = ( .DELTA. C .DELTA. S ) .DELTA. L = 0 .DELTA. S + (
.DELTA. C .DELTA. L ) .DELTA. S = 0 .DELTA. L ##EQU00001## [0024]
(1) when the substrate is not being bent, .DELTA.C=0, C
.quadrature. C.sub.un-bend; [0025] (2) when the substrate is being
bent along an orthogonal base in two-dimensional space, e.g., along
Y axis, the distance S is increased (the length L remains
constant), and accordingly, the overall capacitance is decreased.
The capacitance at this time is C.sub.Trad.,Y-bend.
[0025] .DELTA. C Trad . , Y - bend = ( .DELTA. C .DELTA. S )
.DELTA. L = 0 .DELTA. S ##EQU00002## since , ( .DELTA. C .DELTA. S
) < 0 and .DELTA. S > 0 ##EQU00002.2##
then, .DELTA.C.sub.Trad.,Y-bend<0
C.sub.Trad.,Y-bend=C.sub.un-bend+.DELTA.C.sub.Trad.,Y-bend<C.sub.un-b-
end
and C.sub.min..ltoreq.C.sub.Trad.,Y-bend<C.sub.un-bend wherein
C.sub.min. is the absolute minimum value of capacitance bent along
Y axis; [0026] (3) when the substrate is bent along another
orthogonal base in two-dimensional space, e.g., along X axis, the
length L is increased (the distance S remains constant), and
accordingly, the overall capacitance is increased. The capacitance
at this time is C.sub.Trad.,X-bend.
[0026] .DELTA. C Trad . , Y - bend = ( .DELTA. C .DELTA. L )
.DELTA. S = 0 .DELTA. L ##EQU00003## since , ( .DELTA. C .DELTA. L
) > 0 and .DELTA. L > 0 ##EQU00003.2##
then, .DELTA.C.sub.Trad.,X-bend>0
C.sub.Trad.,X-bend=C.sub.un-bend+.DELTA.C.sub.Trad.,X-bend>C.sub.un-b-
end
and C.sub.un-bend.ltoreq.C.sub.Trad.,X-bend<C.sub.max., wherein
C.sub.max. is the absolute maximum value of capacitance bent along
X axis.
[0027] From (2) and (3), that the range of capacitance is
.DELTA.C.sub.Trad,bend when the conventional interdigital capacitor
is bent along X axis or Y axis is:
.DELTA.C.sub.Trad,bend=|C.sub.max.-C.sub.min.|
[0028] The interdigital capacitor of the present embodiment employs
coupling electrodes of more than one direction, and thus results in
more stable capacitance when the substrate is bent. What follows
will take the interdigital capacitor of the present invention shown
in FIG. 2 as an example to demonstrate the variation on electrical
characteristics when the substrate is bent. The interdigital
capacitor in this embodiment has coupling electrodes of Y direction
and X direction. Hence, the distance S and the length L may change
simultaneously when the capacitor is bent along Y axis or X
axis,
and since
( .DELTA. C .DELTA. S ) < 0 , .DELTA. S > 0 , ( .DELTA. C
.DELTA. L ) > 0 , .DELTA. L > 0 ##EQU00004##
Therefore, compensation occurs to the capacitance (C.sub.New,bend)
after the capacitor is bent, due to the change of distance S and
length L; the range of capacitance now is .DELTA.C.sub.New,bend. In
practice, the number of coupling electrodes along Y direction and X
direction can be adjusted so as to make .DELTA.C.sub.New,bend=0,
which means the capacitance remains the same after the capacitor is
bent. On the other hand, the number of coupling electrodes can be
adjusted so as to make
.DELTA.C.sub.New,bend<.DELTA.C.sub.Trad,bend, which means the
capacitance remains relatively stable after the capacitor is
bent.
[0029] In the above-mentioned embodiment, the interdigital
capacitor is a type of interdigital capacitor which can be embedded
within a substrate. The couplings therein are not in one direction,
and therefore, the capacitor can have coupling electrodes of more
than two directions at the same time. This enables the interdigital
capacitor to have more stable capacitive characteristics and less
variation on electrical characteristics after being bent. Also,
this feature can prevent the high-frequency characteristics of a
capacitor from changing vastly, which results in impedance mismatch
that may influence electrical performance of a system module. Since
capacitors are widely used in high-frequency circuits such as those
applied to low noise amplifiers, variable-gain amplifiers and power
amplifiers, the overall performance of system circuits can be
improved if impedance mismatches are reduced. The interdigital
capacitors of the present embodiments, then, can be further applied
to a variety of modules or products with flexible high-frequency
circuits.
[0030] With the interdigital capacitor of the present embodiments,
the number and shape of the coupling electrodes can be adjusted
according to the bending direction of the substrate. This enables
the capacitor to have more stable capacitive characteristics and
less variation on electrical characteristics; the feature overcomes
disadvantages of a conventional interdigital capacitor which
includes a coupling electrode structure of only a single direction.
The capacitive characteristics of a conventional interdigital
capacitor is subject to change in accordance with the bending
direction, which may result in a vast change in electrical
characteristics when the electrode structure encounters an external
bending force.
[0031] The aforementioned embodiments of the present invention
would be understood by those skilled in the art. Any change or
modification or the equivalent thereof can be made without
departing from the spirit of the following claims. Moreover, the
present invention is not limited within the scope of the
aforementioned embodiments. For example, the coupling electrodes
extending from the first extending electrode and the second
extending electrode of the present embodiments can be provided in
different shapes or numbers based on the actual needs; the
plurality of coupling electrodes can be, for example,
geometric-shaped like rectangular-shaped, circular-shaped,
triangular-shaped, taper-shaped or oval-shaped; and the plurality
of first extending electrodes and second extending electrodes can
be disposed in a parallel or non-parallel manner.
* * * * *